the boston marathon bombers as brothers, tamerlan and dzhokhar tsarnaev. they are from a predominantly muslim region in russia. the 19-year-old brother believed to be extremely dangerous possibly armed with explosives on his person. unclear whether he was injured in the shoot outlast night in which his 26-year-old brother died. it's unclear whether he's injured and hiding somewhere and unable to move, whether he moved, they don't know right now. we're told that the brother was wearing explosives and a triggering device when he died which is why they're worried -- >> the older brother. >> the older brother. this is why they're worried the younger brother could be in a similar situation. this happened overnight and intensified. police say the suspects robbed a convenience store, shot and killed an m.i.t. police officer. i was on the air live when that happened last night, wolf. and as you know, it was no expectation at that time that there was any relation between the two things. but there ended up being. >> and when they heard of a convenience store robbery, stuff like that happens. >> right.